US20220328377A1 - Power semiconductor component and method for producing a power semiconductor component - Google Patents

Abstract

A power semiconductor component is specified, having a power semiconductor device arranged within a housing, wherein a heat sink is exposed on a first surface of the housing; a wiring substrate which receives the housing with the power semiconductor device and which has a first main surface and a second main surface. A heat dissipation region with increased thermal conductivity is arranged on the second main surface. The housing is arranged on the wiring substrate in such a way that the heat sink is connected to the heat dissipation region via a solder layer. A number of spacers which are arranged between the heat sink and the heat dissipation region are embedded in the solder layer. Furthermore, a method for producing a power semiconductor component is specified.

Description

CROSS REFERENCE TO RELATED APPLICATIONS
• This application is the U.S. National Phase Application of PCT International Application No. PCT/EP2020/078019, filed Oct. 6, 2020, which claims priority to German Patent Application No. 10 2019 215 503.0, filed Oct. 10, 2019, the contents of such applications being incorporated by reference herein.
FIELD OF THE INVENTION
• The present invention relates to a power semiconductor component having a power semiconductor device arranged within a housing, and also to a method for producing a power semiconductor component.
BACKGROUND OF THE INVENTION
• Power semiconductor devices such as for example MOSFETs are arranged in housings, typically plastic housings, with cooling surfaces, for example made of copper, exposed on the outer side of the housing, there being a number of different housing designs, such as for example D2PAK, DPAK, TO220, etc. The devices are designed in some instances as surface-mountable devices and in some instances as through-hole-mountable devices. Said devices typically have at least two connection pins which are led out of the plastic housing and which can be connected to connections of a wiring substrate.
• Since power semiconductor components having such power semiconductor devices emit large quantities of heat during operation, the efficient dissipation of this heat is a particular challenge. Typically, the heat is dissipated via the wiring substrate on which the packaged power semiconductor device is arranged. To this end, said wiring substrate may have thermal bores (vias), for example. Such a power semiconductor component is known from JP 2018-120991 A, incorporated herein by reference.
• DE 11 2016 005 508 T5, incorporated herein by reference, also discloses the dissipation of heat via vias that can be completely or partially filled with solder. According to one embodiment, a solder resist which is applied around the vias and onto which the power semiconductor device is placed can prevent solder from flowing into the vias.
• In some more recent applications, for example in chargers used in electric vehicles, very high power losses occur, such that cooling is of particular importance. In some instances, the use of thermal bores is also not possible in such applications due to electrical insulation regulations.
SUMMARY OF THE INVENTION
• Therefore, an aspect of the present specifies a power semiconductor component which has a particularly effective dissipation of heat emitted by the power semiconductor device. It is also intended to specify a method for producing such a power semiconductor component.
• According to one aspect of the invention, a power semiconductor component which has at least one power semiconductor device arranged within a housing is specified, wherein a heat sink is exposed on a first surface of the housing. The housing is in particular a plastic housing. The heat sink is formed in particular from metal. The housing may for example have substantially a cuboid shape.
• The power semiconductor component also has a wiring substrate having a first main surface and a second main surface. The wiring substrate may in particular be a PCB substrate, that is to say a printed circuit board. In this case, the power semiconductor component is in particular a circuit board arrangement. A heat dissipation region with increased thermal conductivity is arranged on the second main surface. For example, the heat dissipation region is formed by a copper layer of the circuit board, said copper layer being arranged on the second main surface of the wiring substrate.
• The housing is arranged on the wiring substrate in such a way that the heat sink is connected to the heat dissipation region via a solder layer. A number of spacers which are arranged between the heat sink and the heat dissipation region are embedded in the solder layer. The spacers are particularly advantageously formed from a material that has good electrical and thermal conductivity.
• The spacers may in particular be SMD adhesive spots, that is to say quantities of SMD adhesive applied in a punctiform manner. An SMD adhesive is understood here to mean an adhesive which is used to fix surface-mountable components (surface-mount devices). Such adhesives, which may for example be electrically conductive adhesives based on epoxy resin, are known in principle to those skilled in the art and are therefore not explained in more detail at this point. The SMD adhesive spots can be arranged directly on the material of the heat dissipation region or on a solder resist web applied to the heat dissipation region.
• The power semiconductor component has the advantage that, by using the spacers, a greater distance can be achieved between the housing and the wiring substrate, so that a thicker solder layer can be applied between the housing and the wiring substrate. This greatly increases the quantity of solder and thus the mass of material with good thermal conductivity on the wiring substrate. It can be increased in particular by one and a half times or can even be more than doubled. In this way, the heat is dissipated particularly effectively from the power semiconductor device and emitted to the environment.
• In addition, the large quantity of material with good thermal conductivity in thermal contact with the heat sink constitutes a buffer in order to absorb temporary power peaks of the power semiconductor device that bring about a temporary rise in temperature.
• The housing with the semiconductor device is arranged on the second main surface of the wiring substrate in such a way that the heat sink is arranged completely on the heat dissipation region and is connected thereto via a solder layer.
• In addition, the thickness of the heat dissipation region can also be increased. Typically, with standard circuit board technology, a maximum of 70 micrometers of copper is available per layer, in some instances even up to 105 micrometers or up to 201 micrometers. This maximum thickness can be fully exploited for the heat dissipation region in order to maximize the heat-conducting mass.
• According to one embodiment, the material forming the heat dissipation region, in particular copper or a copper alloy, is embedded in a matrix made of plastics material of the wiring substrate, and the surface of the heat dissipation region is thus coplanar with the rest of the surface of the wiring substrate. Alternatively, the heat dissipation region could also rest on a surface of the wiring substrate.
• According to one embodiment, the power semiconductor device arranged in the housing is designed to be through-hole-mountable. In this embodiment, the power semiconductor device has connection pins which protrude from the housing and which are intended to be plugged into through-holes of the wiring substrate. Said connection pins are then soldered there. In this embodiment, it is possible to use the vias (through-holes) of the wiring substrate to introduce a large quantity of solder material between the heat sink and the heat dissipation region of the wiring substrate. According to one embodiment, the wiring substrate therefore has a number of vias in the heat dissipation region, through which vias the solder material is introduced between the heat sink and the heat dissipation region of the wiring substrate. In the case of such a wiring substrate, the spacers are applied between the vias so that they do not cover them.
• This embodiment has the advantage that a large quantity of solder can be pumped under the housing using a THT (through-hole technology) soldering process. This makes it possible to achieve a high thickness of the solder layer, which would be possible only with difficulty in the case of a printed-on solder layer.
• According to an alternative embodiment, the power semiconductor device arranged in the housing is designed to be surface-mountable. In this embodiment, connection pins also protrude from the housing, but are provided for soldering onto contact connection areas on the wiring substrate and not for plugging into through-holes.
• In this embodiment, vias can nevertheless be provided in order to bring solder material under the housing. Alternatively, however, the housing with the power semiconductor device can be connected to the heat dissipation region by means of a solder wire or solder wire pieces after fixing by means of the spacers. In this embodiment, the solder layer is therefore introduced into the intermediate space between the housing and the heat dissipation region not by printing or pumping but by inserting pieces of solder wire. This embodiment also makes it possible to achieve a considerable thickness of the solder layer and thus a large heat-conducting mass.
• According to one embodiment, the heat sink has an area a on the first surface and the heat dissipation region has an area A on the second main surface, where a <A applies. In particular, a <0.75 A or even a <0.5 A may apply. This embodiment has the advantage that the quantity of heat-conducting material is increased due to the large area of the heat dissipation region. In addition, the large heat dissipation region, which protrudes laterally beyond the housing with the power semiconductor device, achieves a particularly good heat spread. The dissipation of heat to the environment is thus improved.
• According to one aspect of the invention, a method for producing the described power semiconductor component is specified, said method comprising providing a power semiconductor device arranged within a housing, wherein a heat sink is exposed on a first surface of the housing. A wiring substrate having a first main surface and a second main surface is also provided, wherein a heat dissipation region with increased thermal conductivity is arranged on the second main surface.
• A number of spacers are applied to the wiring substrate in a mounting region of the heat dissipation region, and the housing with the power semiconductor device is placed onto the spacers in the mounting region. A solder material is introduced into an intermediate space between the heat sink and the heat dissipation region.
• The region provided for receiving the housing with the power semiconductor device is referred to as the mounting region. It thus corresponds in terms of shape and extent to the first surface of the housing to be applied.
• The introduction of solder material can be effected in through-hole technology by means of vias arranged in the wiring substrate. Alternatively, it can also be effected by introducing pieces of solder wire into the intermediate space between the heat sink and the heat dissipation region.
• For example, adhesive spots of an SMD adhesive can be used as spacers.
• The method has the advantage that it allows a particularly large quantity of solder to be applied to the heat dissipation region. This makes it possible to achieve solder layer thicknesses that could not be achieved, or could be achieved only with difficulty, with standard printing processes. In this way, a particularly large quantity of material with good thermal conductivity is brought into contact with the heat sink.
BRIEF DESCRIPTION OF THE DRAWINGS
• Embodiments of the invention will be described by way of example below with reference to schematic drawings.
• FIG. 1 schematically shows a power semiconductor component according to one embodiment of the invention in cross section, and
• FIG. 2 schematically shows the power semiconductor component as perFIG. 1 in a plan view.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Thepower semiconductor component1 as perFIG. 1 has apower semiconductor device2, of which only aplastic housing4 is shown inFIG. 1, and also connection pins24 protruding from theplastic housing4 and aheat sink6 exposed on a first surface5 of thehousing4. Thepower semiconductor device2 additionally has at least one power semiconductor chip, for example a MOSFET, which is thermally and possibly also electrically connected to theheat sink6. Thepower semiconductor device2 is electrically contact-connected via the connection pins24 and possibly via theheat sink6.
• The embodiment shown is a through-hole-mountablepower semiconductor device2. Alternatively, however, it could also be a surface-mountable power semiconductor device.
• Thepower semiconductor component1 also has awiring substrate10 which, in the embodiment shown, is designed as a PCB substrate and has a firstmain surface12 and a second main surface14 situated opposite the latter. Thewiring substrate10 comprises substantially a matrix made of plastic, in whichcontact connection areas18 for the connection pins24, conductor tracks (not illustrated) and aheat dissipation region16 made of copper are embedded. Theheat dissipation region16 is exposed on a second main surface14 of thewiring substrate10 and is provided for receiving thepower semiconductor device2 and for establishing thermal (and possibly also electrical) contact with theheat sink6.
• Thewiring substrate10 has a number ofvias25,26. In this case, vias25 in the region ofcontact connection areas18 are provided as electrical vias through which the connection pins24 are led.Vias26 in the region of theheat dissipation region16 are embodied as thermal vias and are used, among other things, to dissipate heat.
• Asolder layer20 for the electrical and mechanical connection of thepower semiconductor device2 and thewiring substrate10 is applied both to theheat dissipation region16 and to the contact connection areas8. Thepower semiconductor device2, in particular theheat sink6, is connected to theheat dissipation region16 in an electrically and thermally conductive manner via thesolder layer20. The connection pins24 are connected to thecontact connection areas18 in an electrically and thermally conductive manner via thesolder layer20.
• Thesolder layer20 has a high thickness d. It is therefore not printed, as is otherwise usually customary, onto thewiring substrate10. Rather, thehousing4 with thepower semiconductor device2 is first placed onto theheat dissipation region16, and fixed there, by means ofspacers28 which are SMD adhesive spots in the embodiment shown. Thehousing4 or theheat sink6 exposed on its first surface5 is then soldered to theheat dissipation region16 by means of through-hole technology. In this case, solder material for thesolder layer20 is introduced from the firstmain surface12 through thevias26 into the intermediate space between theheat sink6 and thewiring substrate10. At the same time, thesolder layer20 can also be applied to thecontact connection areas18 through thevias25. However, since this does not have to have a particularly great thickness, it can also be printed on using a standard process.
• Here, the quantity of solder and the pressure with which the solder is brought into the intermediate space are controlled in such a way that thesolder layer20 fills substantially the entire intermediate space between theheat sink6 and thewiring substrate10. Thevias26 can also be filled with solder material or they can be kept free or filled with another material which preferably has good thermal conductivity.
• FIG. 2 shows thepower semiconductor component1 in a plan view. It can be seen in this view that theheat dissipation region16 has a significantly larger areal extent than thehousing4 or theheat sink6, which is not visible inFIG. 2. In the embodiment shown, the area A of theheat dissipation region16 is more than twice as large as the area a of theheat sink6 that is exposed on the first surface5 of thehousing4.
• As can be seen inFIG. 2, theheat dissipation region16 thus protrudes laterally to a significant extent beyond thehousing4. In the embodiment shown inFIG. 2, said heat dissipation region protrudes beyond thehousing4 on all sides.
• The copper material of theheat dissipation region16 and also the solder material of thesolder layer20 form an increased thermal mass, which can both buffer temporary temperature increases due to power peaks and, owing to its large spatial extent, can achieve a good heat spread.

Claims (11)

1. A power semiconductor component, comprising:

a power semiconductor device arranged within a housing, wherein a heat sink is exposed on a first surface of the housing; and

a wiring substrate which receives the housing with the power semiconductor device and which has a first main surface and a second main surface, wherein a heat dissipation region with increased thermal conductivity is arranged on the second main surface;

wherein the housing is arranged on the wiring substrate in such a way that the heat sink is connected to the heat dissipation region via a solder layer, wherein a number of spacers which are arranged between the heat sink and the heat dissipation region are embedded in the solder layer, and

wherein the spacers are formed from a material that has good electrical and thermal conductivity.

2. The power semiconductor component as claimed inclaim 1, wherein the power semiconductor device arranged in the housing is designed to be through-hole-mountable.

3. The power semiconductor component as claimed inclaim 1,

wherein the wiring substrate has a number of vias through which the solder material is introduced between the heat sink and the heat dissipation region of the wiring substrate.

4. The power semiconductor component as claimed inclaim 1,

wherein the power semiconductor device arranged in the housing is designed to be surface-mountable.

5. The power semiconductor component as claimed inclaim 1,

wherein the housing with the power semiconductor device is electrically connected to the heat dissipation region by means of the spacers and by means of a solder layer.

6. The power semiconductor component as claimed inclaim 1,

wherein the heat sink has an area a on the first surface and the heat dissipation region has an area A on the second main surface, where a <A applies.

7. A method for producing a power semiconductor component as claimed inclaim 1, comprising the following:

providing a power semiconductor device arranged within a housing, wherein a heat sink is exposed on a first surface of the housing;

providing a wiring substrate having a first main surface and a second main surface, wherein a heat dissipation region with increased thermal conductivity is arranged on the second main surface;

applying a number of spacers to the wiring substrate in a mounting region of the heat dissipation region, and placing the housing with the power semiconductor device onto the spacers in the mounting region;

subsequently introducing solder material into an intermediate space between the heat sink and the heat dissipation region.

8. The method as claimed inclaim 7,

wherein solder material is introduced by means of vias arranged in the wiring substrate.

9. The method as claimed inclaim 7,

wherein solder material is introduced by introducing pieces of solder wire.

10. The method as claimed inclaim 7,

wherein adhesive spots of an SMD adhesive are used as spacers.

11. The power semiconductor component as claimed inclaim 2, wherein the wiring substrate has a number of vias through which the solder material is introduced between the heat sink and the heat dissipation region of the wiring substrate.

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